Exciter differential field control



Spt. 8, 1931. w. B. JUPP 1,822,150

EXCII'ER DIFFERENTIAL FIELD CONTROL;

Filed June 13. 1929 Load Mum/boa: Mllq'am EJ Patented Sept. 8, 1931PATENT OFFICE I WILLIAM B. STUFF, NEW YORK. N. Y., ASSIGNOB 'IOINTEBNATIONLL IO'IOB 001- A PANY,. OF NEW YORK, N. Y., A CORPORATION OFDELAWARE EXCIIEB. DIFFERENTIAL FIELD CONTROL Application filed June 13,

The present invention relates to a field controlling mechanism for agenerator and embodies, more specifically, an improved device forcontrolllng the field of a generator power units, an internal combustionengine drivesa generator which supplies power to driving motors. Bestoperation is had when the generator is separately excited and,therefore, an exciter is provided having a differentially compoundedfield. The series field of the exciter is connected in series with themain generator in order that the generator load may exert a propereffect upon the excitation of the exciter field.

In the above described hook-up of units, as the generator outputincreases, the strength of the exciter differential field increases,thus weakening the exciter field and reducin its voltage. 1- Thisreduces the excitation o the main generator fieldikand thus also reducesthe output of the generator and the load on the internal combustionengine.

When the generator is cold, as in starting up, it frequently happensthat the engine hasnt sufficient power to cause the generator to supplysufiicient current to the differential field to produce the desiredweakening effect in order that the generator load may be reduced topermit the engine to build up. Under these conditions, satisfactoryoperation is not had and the present invention is designed to overcomethese difiiculties.

An object of the invention therefore is to provide a means forpermitting the load of the generator to be decreased automatically,

thus enabling the en ine to build up.

A further object 0% the invention is to provide a means for reducing theexciter output and to decrease the generator load in accordance with thebuilding up of the engine.

A further object of the invention is to provide a means for controllingthe field strength 1929. Serial R0. 870,492.

of the exciter in acocrdance with the speed of the internal combustionengine.

A further ob'ect of the invention is to rovide a means or automaticallycontrolling the exciter differential field in accordance with the torquesupplied by the internal combustion engine.

Further objects, not specifically enumerated above, will be apparent asthe inven-- tion is described in reater detail in connection with thesingle gure of drawing, wherein is shown, dia rammatically, theconnection of the exciter differential field to a resistance which iscontrolled b suitable relays which are in turn controlle by the speed ofrotation of the internal combustion engine.

Referring to the above drawing, a indicates a suitable shaft, forexample, the timing shaft, which is driven directly from the internalcombustion engine and upon which are mounted spaced switch discs a and(1 respectively. he discs are formed of outer conducting disc sections aand inner insulatmg disc segments a. Brushes a engage the r-ipheries ofdisc elements a on disc a and rushes a engage the peripheries of discelements a on disc a.

Between the switch discs (1 and a an inertia disc I) is mounted. Thisdisc is pivoted at 1) upon shaft a and is normally held in the positionshown in the drawin b a spring 12 which is connected between t e isc aand the lower portion of the disc 6. Conducting segments 1) are formedon the disc I) and contacts a, connected to the outer disc elements a onthe disc a, are positioned to be engaged by one of the segments 1) whenthe disc is in the position shown in the drawing. Contacts a connectedto the outer disc elements a of the disc a are positioned so that theywill be engaged by the conducting segments 6 when the disc is in'asubstantially vertical position.

For engine speeds up to 1400 revolutions per minute, the spring 6 holdsthe disc in the position shown in the drawing. The tension of thisspring is so adjusted that an engine speed of 1600 revolutions perminute causes the left hand conducting segment b to engage the contactsa Between these limits,

, wire to a relay 6,

' e. The other contacts of the disc I) engages neither set of contacts.A current source 0 is connected through wire 0 to the inner contacts aand (1. The outer contact a is connected through Wire 0 to a rela (l andwire 0 connects the other terminal 02 the relay to the current source 0.The outercontact a is connected through the other terminal of the relaybeing connected to wire a. It will thus be seen that relay d isenergized when contacts a are engaged by the disc, while relay e isenergized when contacts a are engaged by the system.

The contacts of relay 6 are normally open while those of relay d arenormally closed, although for speeds below 1400 revolutions per minute,relay (1 is energized to open its contacts. A resistance R is connectedthrough wire d with one of the contacts of relay (1 while, at the otherend of the resistance, wire '6' connects it to one of the contacts ofrelay the relays d and e are connected to an intermediate oint of theresistance R through a wire f, t us dividing the resistance R intoresistance units 1" 1nd 1'.

The main generator is shown at G, having a shunt field g. An exciter Eis connected to the generator shunt field through wires g? and providedwith a shunt field h. Thedifierential field of the exciter is shown at Dand is connected in series with the generator and motor through wires,h. Resistance R is connected across the differential field D by meansof wires h The operation of the device is as follows For engine speedsbelow 1400 revolutions per minute, contacts a are closed and relay, (1energized, thus cutting in resistance element 1' and causing greaterexcitation of the differential fields, thereby weakening the excitershunt fields and reducing the load. This reduction in excitation permitsthe engine speed to increase, thereby increasing the eneratoroutput inproportion to the engine H. P. increase, due to increased speed.

As the motor accelerates, it will require higher voltage and the enginespeed will increase. The disc 6 will move away from contacts a,deenergizing relay (1 and thus closin its contacts and cutting outresistance r. Tfiis will weaken the differential fields, therebyincreasing the exciter fields, thus tending normally to increase thegenerator load, this actionbeing minimized by continned reduction ofamperes caused by the motor acceleration.

As the engine accelerates, contacts a will be closed, energizingcontactor e and cutting q out resistance r, thereby decreasing theexcitation in the differential fields and allow ing increased excitationin the exciter and main generator shunt fields, thus tending to preventfurther increase of the engine speed due to the increase in generatorload.

While the invention has been described with specific reference to theconnections shown in the accompanying drawing, it is not to be limited,save as defined. in the appended claims.

I claim as my invention:

1. In combination with.an exciter difierential field and a speedresponsive switch, a resistance connected across the field, a normallyopen relay connected across a portion of the resistance,opposed contactscooperating with the switch, into engagement with one of connectionsbetween one of the contacts and the relay, a second relay normallyclosed across a second portion of the resistance, and connectionsbetween the secondrelay and the other of the spaced contacts.

2. In combination with an exciter field and a speed responsive switch, aresistance connected across the field, relays connected across portionsof the resistance, opposed contacts cooperating with the switch, meansto urge the switch into engagement with one of the contacts, andconnections between the contacts and relays.

3. In combinatlon with a generator and an engine for driving the same, agenerator field, a switch normally urged into engagement with one set ofcontacts, but actuated by a predetermined engine speed to engage asecond set of contacts, a resistance across the field, relays acrossportions of the resistance, and means connecting the relays to the contacts to cut in the reistance when the switch engages the secondcontacts, to cut in one portion of the resistance when the switchengages neither set of contacts, and to cut out the resistance when theswitch engages the first contacts. 1 4. In combination with engine fordrivin the same, a generator field, a switch normal y urged intoengagement with one set of contacts, but actuated by a predeterminedengine speed to engage a second set of contacts, a resistance across thefield, relaysacross portions of the resistance, and means connectm therelays to the contacts to cut in the reslstance when the switch engagesthe second contacts and to cut out the resistance when the switchengages the first contacts.

5. In combination with a generator and an engine for'driving the same, agenerator field, an engine speed ance across the field, relays acrossportions of the resistance, and means controlled by the speed responsivedevice to operate the reays.

This s cification June A. 1929.

WILLIAM B. JUPP.

a generator and an signed this 7th day of responsive device, aresistmeans to urge the switch the contacts,

